"I ALWAYS WANTED to be a piano player," says Bob Diener, who recently celebrated his fourth anniversary at the piano bar in the Riverfront Lounge of Charlie's Georgetown. The 24-year-old pianist has been a professional for nearly a decade -- he was playing weddings, bar mitzvahs and even club dates while a student at Springbrook High School in Silver Spring, where he grew up. "I'd get home about 4 in the morning and get up and go to school at 6," he recalls in disbelief.

Even then Diener had 10 years of keyboard study, mostly self-instruction, behind him. "My father and brother played the piano," he explains, "and I used to listen and then copy what they were doing. I have perfect pitch, and it really kind of freaked them out because I could hear them playing something and fool around and play exactly what they were playing."

Inevitably, formal lessons were urged upon the 6-year-old prodigy, and he was placed with "one of those elementary school piano teachers" who taught him the rudiments of reading music. "But I got very bored with it after a couple of months," Diener says, "because it turned out to be one of those courses where they give the kids little ditties to play, and I was trying to figure out 'A Foggy Day in London Town' using ninth inversions that Oscar Peterson uses."

The issue of studying music "properly" continued to surface, eventually joining forces with the notion that while "music can make a great sideline," a young man must settle down to a profession. "When I refused to study in the way he wanted me to," Diener says, "my father did something that I think was great -- he forbade me to play the piano for one month. I was about 10, and not being able to touch the piano for that period of time drove me crazy enough that I just had to go to him and say, 'Look, I don't know what I'll have to do, but I'll do it.' " The outcome was several months of classical training that Diener "didn't really get into." Later he attended the University of Maryland for five semesters "to find, quote unquote, something I would fall in love with," pursuing serial majors in engineering, economics, accounting, history and general studies. "That was when I decided that this was what I had to do," he says.

Diener has also studied with pianist John Eaton, who has played area bistros and eateries for three decades. Last year he had the opportunity to pick up some additional pointers when Oscar Peterson, in residence at Charlie's for a week, gave his longtime admirer a private lesson. Indeed, Diener credits Charlie's -- where he is at the piano from 9 to 1 every night except Mondays, currently joined by singer Debbie Harris Thursdays through Sundays -- with affording him "the exposure to the different artists that have come through there," a number of whom have sat in with him.

Although he reads music easily, to this day Diener prefers trusting his ear when learning a tune. "I'll hear someone doing a song, then I'll go find the original version," he says, "and that's basically how I learn a lot of my material." As for that material, he prides himself on his versatility. Medleys of Gershwin and Ellington, Fats Waller compositions, numbers associated with Nat Cole and Ella Fitzgerald, and Bob Dorough and Dave Frishberg songs are some of the ingredients of a Diener set.

Nor does he look askance at the possibilities of contemporary pop. "There's a great Billy Joel song that I like to do, and I'm just now getting inspired by the Beatles," he says. "I started selecting Lennon-McCartney tunes to put in a medley, things like 'Norwegian Wood,' 'When I'm 64' and 'Eleanor Rigby.' "

Summing up his approach, Diener says that he aims at "presenting music in a quality way, playing a song just different enough that people can recognize their song and still appreciate that it is a fresh approach."